JOHNS HOPKINS / RUTGERS (US) — Infants may not remember what they saw, but they remember that they saw something, according to researchers.

New research reveals that even though very young babies can’t remember details once an object disappears, their brains do retain a notion that whatever they saw was there and still exists.

“This study addresses one of the classic problems in the study of infant development: What information do infants need to remember about an object in order to remember that it still exists once it is out of their view?” says Melissa Kibbe, a postdoctoral researcher in psychological and brain sciences at Johns Hopkins University.

“The answer is, very little.”

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Not long ago, experts believed that babies six months or younger had no sense of “object permanence,” the psychological term that describes an infant’s belief that an object still exists even when it is out of sight.

They thought that if mom or dad wasn’t in the same room with junior, junior didn’t have the sense that his parents were still in the world.

These days, psychologists know that isn’t true: Even for young babies, out of sight doesn’t automatically mean out of mind. But how much do babies remember about the world around them, and what details do their brains need to absorb in order to help them keep track of those things?

The new study, adding a few pieces to the puzzle, was published in the journal Psychological Science. In it, Kibbe and colleague Alan Leslie at Rutgers University found that even though infants cannot remember the shapes of two hidden objects, they are surprised when those objects disappear completely.

The conclusion? Infants do, indeed, remember an object’s existence without recalling what that object is.

This is important, Kibbe explains, because it sheds light on the brain mechanisms that support memory in infancy and beyond.

“Our results seem to indicate that the brain has a set of ‘pointers’ that it uses to pick out the things in the world that we need to keep track of,” says Kibbe, who did the majority of the work on the study while pursuing her doctorate in Leslie’s laboratory at Rutgers.

“The pointer itself doesn’t give us any information about what it is pointing to, but it does tell us something is there. Infants use this sense to keep track of objects without having to remember what those objects are.”

In addition, the study may help researchers establish a more accurate timeline of the mental milestones of infancy and childhood.

In the study, 6-month-olds watched as a triangle was placed behind a screen and as a second object (a disk) was placed behind a second screen. Researchers then removed the first screen to reveal the expected original triangle, the unexpected disk or nothing at all, as if the triangle had vanished completely.

The team then observed the infants’ reactions, measuring how long they looked at expected versus unexpected outcomes.

In the situation where the objects were swapped, the babies seemed to hardly notice a difference, Kibbe says, indicating that they didn’t retain a memory of the original object’s shape. In their minds, a triangle and a disk were virtually interchangeable.

When an object just disappeared, however, and was not replaced by anything, the babies were surprised; they gazed longer at the empty space, indicating that they had expected something to be where something was before.

“In short, they retained an inkling of the object,” Leslie says.

The research was supported by the National Science Foundation.
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